a) Field of the Invention
The invention is directed to a process for cleaning surfaces by means of at least one particle-removing work implement and to a device for carrying out the process.
b) Description of the Related Art
Facades which are soiled by environmental influences such as deposited soot particles or which are covered with unwanted layers of paint are cleaned by methods of mechanical abrasion, preferably by dry blasting. The blasting material is preferably composed of minute round flexible beads of glass which are sprayed onto the surface to be cleaned with a slight spin so as to eradicate the layer of dirt. The blasting material and dirt particles are sucked out by a vacuum system and fed to a dust extracting system which separates the blasting material from the dirt. In order to minimize the formation of dust and the release of blasting material into the surrounding area, blasting and suction are effected in an outwardly closed space whose unique open side tightly contacts the surface to be cleaned.
The cleaning personnel must monitor the blasting action so as to direct the blast onto the soiled regions until the desired degree of cleanliness is achieved. There are two known solutions for providing the visibility required for this monitoring. The first solution consists in providing a closed space which is sufficiently large to accommodate the cleaning personnel. In the second solution, the selected dimensions of the closed space are small enough to be held in the hand of the cleaning personnel and guided along the surface.
The first solution has the disadvantage that the work space for receiving the cleaning personnel which contacts the facade at its open side and is displaced from one area of the facade to another is very large and accordingly also extremely heavy. A crane truck is used to move along the facade, the work space being suspended from its boom. Because of technical factors relating to insurance, this type of suspended attachment for a manned work space is only permissible in conjunction with a special, very expensive crane truck. In addition, the high concentrations of dirt and blasting material in the work space constitute a danger to the eyes and breathing passages of the cleaning personnel. The health hazard can be reduced to a tolerable level only by wearing safety glasses, masks and protective suits. The safety measures do not provide complete protection and also impede work.
Visibility is substantially impaired when working in a closed work space due to the absence of sufficient daylight and due to the high proportion of dust. Owing to this lack of visibility, the cleaning results cannot be satisfactorily monitored. Another unsatisfactory aspect of a closed work space is the lack of direct communication to the outside, in particular to the crane truck. The required two-way communication systems can be employed only with poor results due to the high noise level in the work space. The isolation of the cleaning personnel in an extremely unpleasant working atmosphere is detrimental to work morale and accordingly undercuts the efficiency of the cleaning process. In addition, the closed working space necessitates high costs in equipment and personnel so that cleaning costs are very high.
The disadvantage of the second solution consists in that the closed space or working box containing the blasting nozzle or jet nozzle and suction connection must be held by hand and guided along the surface manually. The required freedom of movement along the surface prevents an adequate sealing at the open side against the surface so that dirt particles and blasting material escape, resulting in a threat to the environment and especially to the health of the personnel carrying out the cleaning. The impact of the blasting jet on the surface cannot be observed in the closed space so that it is not possible to control cleaning of soiled locations in a satisfactory manner. Also, the work box must first be shifted before the cleaning action can be inspected so that the cleaning process is very cumbersome.